The contingency table

For evaluating the utility aspect of forecasts it is often convenient to present the verification in a contingency table with the corresponding hits (H), false alarms (F), misses (M) and correct no-forecasts (Z). If N is the total number of cases then N=H+F+M+Z. The sample climatological probability of an event occurring is then P_clim=(H+M)/N.

Table 2

A wide range of verification scores ^[2] can be computed from this table, but here we will only mention the Hit Rate HR=H/(H+M) and the false alarm rate FR=F/(Z+F) [3].